JPH06158590A - Coating for paper and paper board - Google Patents

Abstract

PURPOSE:To provide the inexpensive coating high in hiding power and in flow characteristics. CONSTITUTION:The coating containing a pigment and a binder as main components is characterized by containing 20-40 pts.wt. of heavy calcium carbonate and 20-40 pts.wt. of spindle-like calcium carbonate among 100 pts.wt. of the pigment. The inexpensive structured kaolin high in its hiding power can be used, and the flow suitability which is the defect of the kaolin can be improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to paper and paperboard paints.

[0002]

2. Description of the Related Art White paperboard is a multi-layered cardboard with 3 to 9 layers and has been used for a long time in various packaging boxes. From the cost requirement and the resource saving requirement, waste paper pulp is used for the middle layer. The middle-ply waste paper pulp is used without being deinked. Virgin pulp or deinked pulp with high whiteness is used for the surface layer. The back layer is the same as the front layer when whiteness is required on both sides, and when it is not necessary, waste paper pulp with low whiteness is used. In order to conceal the color of the middle layer, the surface layer needs to have concealing properties and a certain thickness. However, if concealment is required only on the surface layer,
Since there is a cost problem, it is common to use pulp with a certain degree of whiteness in the lower and upper layers (the layer immediately below the surface layer) so that this layer also has a function of hiding the color of the middle layer. When a more beautiful appearance is required, a paint using a pigment with high whiteness is applied, as in general coated paper for printing. Since the pigment completely hides the formation inside the paperboard, opacity is also required.

On the other hand, paint is often applied to printing paper, and the paint is required to have properties such as printability and whiteness. Further, in recent years, it has been required to make the paper thin, and when the paper is made thin, the opacity of the coating layer is also required.

As described above, it is common for the coating layer of paper or paperboard to be opaque, but in such a case,
Titanium oxide has been conventionally used as a pigment in paints. Titanium oxide has been widely used because it has the highest opacity among pigments, but since it is expensive, pigments to replace it have been developed. Calcined kaolin has been used as a pigment with opacity similar to or close to titanium oxide. For calcined kaolin, hydrous kaolin is 900
It is a bulky aggregate that has a void structure built in by firing at a high temperature of ℃ or higher. However, calcined kaolin has the drawback that it is difficult to disperse and a coating material with a high solid content cannot be obtained.

Therefore, so-called chemically-structured kaolin has been developed which chemically forms aggregates instead of firing.
In the present specification, chemically structured kaolin is hereinafter simply referred to as structured kaolin. Structured kaolin is also a bulky aggregate having a void structure built in like calcined kaolin. For structured kaolin, Paper and Pulp Technology Times 199
It is explained on pages 1-9 of the October 2000 issue. In addition, Japanese Examined Patent Publication No. 59-15944 and Japanese Unexamined Patent Publication No. 63-500.
No. 723, JP-A-62-1757, and JP-A-62-126.
No. 7371 discloses the manufacturing method.

[0006]

Structured kaolin can be dispersed in water at a higher concentration than calcined kaolin, but it is still difficult to obtain a high-concentration coating as compared to conventional hydrous kaolin. The present invention uses structured kaolin to
It is an object of the present invention to provide a coating material having a higher concentration and excellent coating suitability.

[0007]

As a means for solving the above-mentioned problems, the present invention has the following constitution. That is, the present invention relates to a water-dispersed coating composition containing a pigment and a binder as main components, wherein 100 parts by weight of the pigment contains 30 to 30 parts of heavy calcium carbonate.
A water-dispersed paint for paper and paperboard, which comprises 60 parts by weight, 20-40 parts by weight of structured kaolin, and 20-30 parts by weight of spindle-shaped calcium carbonate.

As the structured kaolin used in the present invention, the urea described in JP-B-59-15944 can be used.
Structural aggregates of clay stabilized with formalin polymer, aggregates obtained by precipitating hydrous metal salt silicic acid particles described in Japanese Patent Publication No. 63-500723 onto clay, JP-A-62-1757. Kaolin agglomerated with the described zirconium compounds, JP 62-267
Hydrated kaolin and the like, which are agglomerated with a polyelectrolyte aggregating agent as described in No. 371.

The spindle-shaped calcium carbonate used in the present invention is a precipitated calcium carbonate produced by blowing a gas containing carbon dioxide into an aqueous suspension of calcium hydroxide.
It is a spindle-shaped calcium carbonate having an average major axis of 1 to 5 μm and a major axis / minor axis ratio of 3 to 5. Many methods for producing such spindle-shaped calcium carbonate are known, and are described, for example, in JP-B-54-283399, JP-B-58-43331, and JP-A-3-183618.

In the present invention, structured kaolin is 100% total pigment.
20 parts by weight or more is necessary out of the parts by weight, and if less than 20 parts by weight, the desired improvement in opacity cannot be obtained. Also, 4
If it exceeds 0 parts by weight, the flow characteristics of a high-concentration paint are not good.

In the present invention, the spindle-shaped calcium carbonate is all pigment 1
30 parts by weight or more out of 00 parts by weight is necessary. If it is less than 20 parts by weight, the flow properties of a high-concentration coating material using a pigment containing 20 to 40 parts by weight of structured kaolin are not good. Even if the spindle-shaped calcium carbonate is used in an amount of more than 30 parts by weight, the change in the flow characteristics is saturated, and 20 to 30 parts by weight is optimal in relation to the blending with other pigments.

In the present invention, the heavy calcium carbonate is 30-60.
Parts by weight. Since ground calcium carbonate has high whiteness, is inexpensive, and has good flowability, it is preferable to use as much as possible, but it is inferior in terms of opacity. Since it is necessary to improve the opacity by the structured kaolin and to supplement the poor fluidity of the structured kaolin with the spindle-shaped calcium carbonate, the content of the heavy calcium carbonate is 60 parts by weight or less. If the amount of heavy calcium carbonate is less than 30 parts by weight, the surface strength after coating will be weak.

In the present invention, the binder used together with the pigment is 10 to 20 relative to 100 parts by weight of the pigment in terms of solid content.
Parts by weight. As the binder, a water-soluble polymer substance such as casein, starch and polyvinyl alcohol, or a water-dispersible polymer substance obtained by homopolymerizing or copolymerizing vinyl monomers such as acrylic acid ester, vinyl acetate, styrene and butadiene is used. . The water-soluble polymer substance and the water-dispersible polymer substance are often used in combination.

The total solid content of the binder and pigment in the paint can be appropriately selected from the range of 30 to 80% by weight, but it depends on the application, the type of coater and the like. For example, when coating with a rod coater for paperboard, 50 to 65% by weight is preferable. When coating with a blade coater on gravure printing paper, 55 to 65 wt% is preferable.

If necessary, a dispersant, a viscosity modifier, a water retention agent, a defoaming agent, a water resistance agent, a dye, a pH modifier and the like can be used in the coating material of the present invention.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples. (Example 1) A paint for paperboard was prepared with the following constitution. Pigment structured kaolin 40 parts by weight (Engelhard's Ixilon) Spindle-shaped calcium carbonate 20 parts by weight (Okutama Kogyo Tamapearl 121) Heavy calcium carbonate 40 parts by weight (Dowa Calfine Ace 25) Dispersant Sodium polyacrylate 0 0.5 parts by weight Modified styrene-butadiene latex 13.5 parts by weight Casein 3 parts by weight The above components were mixed and dispersed by a known paint preparation method so that the total solid content concentration was 55%. As for the viscosity of the paint, B-type viscosity and Hercules viscosity were measured, and the results are shown in Table 1.
Shown in.

(Examples 2-3) 30 parts by weight of structured kaolin, 20 parts by weight of spindle-shaped calcium carbonate,
Example 2 was the same as that of Example 1 except that the heavy calcium carbonate was 50 parts by weight. Example 3 was the same as Example 1 except that the pigment composition was 20 parts by weight of structured kaolin, 30 parts by weight of spindle-shaped calcium carbonate and 50 parts by weight of ground calcium carbonate.

(Comparative Examples 1 and 2) A pigment composition was used in the same manner as in Example 1 except that 20 parts by weight of spindle-shaped calcium carbonate was replaced by light calcium carbonate (Tamapearl 222H manufactured by Okutama Kogyo Co., Ltd.). Let's say Example 1. Furthermore, in Comparative Example 1, the secondary kaolin (TH
Comparative Example 2 was prepared in the same manner as Comparative Example 1 except for using CIEBLITE manufactured by IELE.

(Measurement Items) (1) Measurement of B-Type Viscosity The temperature of each paint was adjusted to 30 ° C., and the viscosity was measured with a B-type viscometer manufactured by Tokyo Keiki at a rotation speed of 60 rpm. (2) Measurement of Hercules viscosity Each paint was temperature-adjusted to 30 ° C. and measured with a high shear viscometer manufactured by SMT at a rotation speed of 4400 rpm. (3) Measurement of the whiteness of the paperboard surface after the paperboard coating. The hiding power of the paint was measured by measuring the surface whiteness of the paperboard obtained by applying and drying the paint so that the solid content was 10 g / m ² . Whiteness was measured with a photovolt. All the above measurement results are shown in Table 1.

Table 1 ------------------------------------------------ No. B type viscosity Hercules whiteness viscosity --- ------------------------------------------- Example 1 230 22.6 74.3 Example 2 120 17.5 74. 1 Example 3 120 20.9 73.9 Comparative Example 1 240 25.1 74.2 Comparative Example 2 230 23.4 73.5 --------------------. −−−−−−−−−−−−−−−

[0021]

Industrial Applicability According to the present invention, it is possible to produce a coating composition having a high hiding power and excellent fluidity by using an inexpensive structured kaolin.

Claims (1)

[Claims] 1. A water-dispersed paint containing a pigment and a binder as main components, wherein 30 to 60 parts by weight of heavy calcium carbonate and 20 to 4 of structured kaolin are included in 100 parts by weight of the pigment.
A water-dispersed paint for paper and paperboard, which contains 0 part by weight and 20 to 30 parts by weight of spindle-shaped calcium carbonate.